Method of manufacturing cathode-ray tubes



1954 o. L. VAN STEENIS 2,6 5,477

METHOD OF MANUFACTURING CATHODE-RAY TUBES Filed 001;. 21, 1950 F INVENTOR.

OTTO L. VAN STEENIS AGENT United States Patent METHOD OF MANUFACTURING CATI-IODE-RAY TUBES Otto Louis van Steenis, Eindhoven, Netherlands, assignor to Hartford National Bank and Trust Company, Hartford, Conn., as trustee Application October 21, 1950, Serial No. 191,357

Claims priority, application Netherlands December 19, 1949 1 Claim. (CI. 49-82) The invention relates to methods of sealing a glass window to the glass cone of a cathode-ray tube.

In cathode-ray tubes of the kind comprising a glass cone, the weakest area is found in the transition zone between window and cone, since this zone is subject not only to compression but, at a particular area, also to tensile and shearing stresses in the glass owing to the pressure of the atmosphere. If a separate glass window is sealed to a glass cone, the difliculty arises that the seal between window and cone is then located precisely in the said critical zone, i. e. at the area of the greatest strains. This may be avoided by providing the seal outside the transition zone, for example by using a window with an upright edge. The seal is then located in the peripheral surface outside the rounding of the transition zone between window and cone. Such windows with upright edges may be manufactured by bending over the edge of a flat glass plate or by moulding. However, when bending, a separate operation and frequently a separate jig are involved and moulded windows frequently have faults, such as air bubbles or unevennesses of the surface. It is therefore advantageous to use a window made from a flat disc, for example in the form of a spherically sagged sheet of window glass (i. e. glass free from lead).

A solution of the problem of sealing a sheet of window glass to a glass cone so that the seal is at some distance from the rounding of the transition zone between window and cone is obtained if, according to the invention, in a method of manufacturing a cathode-ray tube comprising a glass window and a glass cone, in which a window made from sheet glass is placed in contact with a glass cone and sealed thereto, the cone and the window are slightly separated during the sealing of the edges, so that the seal becomes located in the peripheral surface of the cone and beyond the bend of the transition zone between window and cone. Consequently, the starting material may then be a slightly spherical, flat glass plate, the edges of which have not been subjected to special treatments, such as are required for the provision of an upright edge although the advantages attendant on the use of such a spherical window are nevertheless obtained.

2,695,477 Patented Nov. 30, 1954 In order that the invention may be readily carried into effect, one example will now be described in detail with reference to the accompanying drawings, in which:

Fig. 1 shows part of a window and a cone prior to scaling;

dFig. 2 shows the same parts subsequent to sealing an Fig. 3 shows diagrammatically an arrangement for carrying out the method according to the invention.

Referring to the figures, 1 designates the wide end of the glass cone which, after the neck is sealed-on, is suspended thereby in a chuck 6 (Fig. 3) over the glass window 2. The cone 1 and the window 2 are then set rotating together and heated, for example, by burners. After the edges of the cone and the window have softened, the window is raised until the said edges engage and are sealed together. The window 2 is then lowered slightly (for example about 5 mms.), so that the seal is stretched and this seal between the glass of the window and the cone becomes located in the peripheral surface of the cone and outside the bend of the transition zone, as is designated in Fig. 2 by 5. By urging the sealing zone from the outside, for example with the use of a thrust roller prior to and during the stretching of the seal, the inner surface of the bend of the transition zone between window and cone may be caused to assume a radius which exceeds the thickness of the screen, and

this is necessary to reduce the strains in the transition zone.

What I claim is:

A method of manufacturing a cathode-ray tube comprising a glass window and a glass cone which comprises the steps of placing the glass window in contact with the glass cone, heating the cone and window to seal the edges thereof, and bending the edge of the window by simultaneously drawing the window slightly apart from the glass cone and exerting pressure externally on the seal while still soft to thereby displace the seal and locate the same in the peripheral surface of the cone outside gs bend of the transition zone between the: window and e cone.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,160,434 Harris May 30, 1939 2,215,644 Hays, Jr. Sept. 24, 1940 2,236,708 Grimditch Apr. 1, 1941 2,334,123 Perkins Nov. 9, 1943 2,389,360 Guyer et al. Nov. 20, 1945 2,581,945 Doran Jan. 8, 1952 FOREIGN PATENTS Number Country Date 536,858 Great Britain May 29, 1941 

